IDL> a = [1,2,!values.F_NAN]
IDL> b= [2,1,1]
IDL> c = fltarr(1,3,2)
IDL> c[*,*,0] = a
IDL> c[*,*,1] = b
IDL> c
1.0000000
2.0000000
NaN
2.0000000
1.0000000
1.0000000
使用mean方法后,需要设置无效值为缺失值,即需要加/NAN,不加NAN的结果如下:
IDL> mean(c,dimension = 3)
1.5000000
1.5000000
NaN
加了NAN的结果如下:
ENVI> c[*,*,0] = a
ENVI> c[*,*,1] = b
ENVI> c[*,*,2] = [2,5,8]
ENVI>
ENVI> c
1.0000000
2.0000000
NaN
2.0000000
1.0000000
1.0000000
2.0000000
5.0000000
8.0000000
ENVI> mean(c,dimension = 3,/NAN)
1.6666666
2.6666667
4.5000000